[llvm-branch-commits] [llvm-branch] r96415 - in /llvm/branches/Apple/Hermes/lib/CodeGen: PHIElimination.h RegAllocLocal.cpp

[Dale Johannesen]

Author: johannes
Date: Tue Feb 16 17:58:29 2010
New Revision: 96415

URL: http://llvm.org/viewvc/llvm-project?rev=96415&view=rev
Log:
Merge recent DBG_VALUE handling patches.
--- Merging r96207 into '.':
U    lib/CodeGen/RegAllocLocal.cpp
--- Merging r96294 into '.':
G    lib/CodeGen/RegAllocLocal.cpp
--- Merging r96318 into '.':
U    lib/CodeGen/PHIElimination.h


Modified:
    llvm/branches/Apple/Hermes/lib/CodeGen/PHIElimination.h
    llvm/branches/Apple/Hermes/lib/CodeGen/RegAllocLocal.cpp

Modified: llvm/branches/Apple/Hermes/lib/CodeGen/PHIElimination.h
URL: http://llvm.org/viewvc/llvm-project/llvm/branches/Apple/Hermes/lib/CodeGen/PHIElimination.h?rev=96415&r1=96414&r2=96415&view=diff

==============================================================================
--- llvm/branches/Apple/Hermes/lib/CodeGen/PHIElimination.h (original)
+++ llvm/branches/Apple/Hermes/lib/CodeGen/PHIElimination.h Tue Feb 16 17:58:29 2010
@@ -109,12 +109,29 @@
     // SkipPHIsAndLabels - Copies need to be inserted after phi nodes and
     // also after any exception handling labels: in landing pads execution
     // starts at the label, so any copies placed before it won't be executed!
+    // We also deal with DBG_VALUEs, which are a bit tricky:
+    //  PHI
+    //  DBG_VALUE
+    //  LABEL
+    // Here the DBG_VALUE needs to be skipped, and if it refers to a PHI it
+    // needs to be annulled or, better, moved to follow the label, as well.
+    //  PHI
+    //  DBG_VALUE
+    //  no label
+    // Here it is not a good idea to skip the DBG_VALUE.
+    // FIXME: For now we skip and annul all DBG_VALUEs, maximally simple and
+    // maximally stupid.
     MachineBasicBlock::iterator SkipPHIsAndLabels(MachineBasicBlock &MBB,
                                                 MachineBasicBlock::iterator I) {
       // Rather than assuming that EH labels come before other kinds of labels,
       // just skip all labels.
-      while (I != MBB.end() && (I->isPHI() || I->isLabel()))
+      while (I != MBB.end() && 
+             (I->isPHI() || I->isLabel() || I->isDebugValue())) {
+        if (I->isDebugValue() && I->getNumOperands()==3 && 
+            I->getOperand(0).isReg())
+          I->getOperand(0).setReg(0U);
         ++I;
+      }
       return I;
     }
 

Modified: llvm/branches/Apple/Hermes/lib/CodeGen/RegAllocLocal.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/branches/Apple/Hermes/lib/CodeGen/RegAllocLocal.cpp?rev=96415&r1=96414&r2=96415&view=diff

==============================================================================
--- llvm/branches/Apple/Hermes/lib/CodeGen/RegAllocLocal.cpp (original)
+++ llvm/branches/Apple/Hermes/lib/CodeGen/RegAllocLocal.cpp Tue Feb 16 17:58:29 2010
@@ -490,9 +490,12 @@
   // If the virtual register is already available, just update the instruction
   // and return.
   if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
-    MarkPhysRegRecentlyUsed(PR);       // Already have this value available!
     MI->getOperand(OpNum).setReg(PR);  // Assign the input register
-    getVirtRegLastUse(VirtReg) = std::make_pair(MI, OpNum);
+    if (!MI->isDebugValue()) {
+      // Do not do these for DBG_VALUE as they can affect codegen.
+      MarkPhysRegRecentlyUsed(PR);       // Already have this value available!
+      getVirtRegLastUse(VirtReg) = std::make_pair(MI, OpNum);
+    }
     return MI;
   }
 
@@ -609,6 +612,8 @@
   DenseMap<unsigned, std::pair<MachineInstr*, unsigned> > LastUseDef;
   for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
        I != E; ++I) {
+    if (I->isDebugValue())
+      continue;
     for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
       MachineOperand& MO = I->getOperand(i);
       // Uses don't trigger any flags, but we need to save
@@ -691,7 +696,13 @@
     bool usedOutsideBlock = isPhysReg ? false :   
           UsedInMultipleBlocks.test(MO.getReg() -  
                                     TargetRegisterInfo::FirstVirtualRegister);
-    if (!isPhysReg && !usedOutsideBlock)
+    if (!isPhysReg && !usedOutsideBlock) {
+      // DBG_VALUE complicates this:  if the only refs of a register outside
+      // this block are DBG_VALUE, we can't keep the reg live just for that,
+      // as it will cause the reg to be spilled at the end of this block when
+      // it wouldn't have been otherwise.  Nullify the DBG_VALUEs when that
+      // happens.
+      bool UsedByDebugValueOnly = false;
       for (MachineRegisterInfo::reg_iterator UI = MRI.reg_begin(MO.getReg()),
            UE = MRI.reg_end(); UI != UE; ++UI)
         // Two cases:
@@ -699,12 +710,26 @@
         // - used in the same block before it is defined (loop)
         if (UI->getParent() != &MBB ||
             (MO.isDef() && UI.getOperand().isUse() && precedes(&*UI, MI))) {
+          if (UI->isDebugValue()) {
+            UsedByDebugValueOnly = true;
+            continue;
+          }
+          // A non-DBG_VALUE use means we can leave DBG_VALUE uses alone.
           UsedInMultipleBlocks.set(MO.getReg() - 
                                    TargetRegisterInfo::FirstVirtualRegister);
           usedOutsideBlock = true;
+          UsedByDebugValueOnly = false;
           break;
         }
-    
+      if (UsedByDebugValueOnly)
+        for (MachineRegisterInfo::reg_iterator UI = MRI.reg_begin(MO.getReg()),
+             UE = MRI.reg_end(); UI != UE; ++UI)
+          if (UI->isDebugValue() &&
+              (UI->getParent() != &MBB ||
+               (MO.isDef() && precedes(&*UI, MI))))
+            UI.getOperand().setReg(0U);
+    }
+  
     // Physical registers and those that are not live-out of the block
     // are killed/dead at their last use/def within this block.
     if (isPhysReg || !usedOutsideBlock) {